What are the base-pairs and hydrogen bonding rule for dna nucleotides

According to Chargaff's rule also known as the base pair rule, the DNA from any cells of all the organisms should exhibit a ratio of 1: 1, that is, the amount of adenine should be equivalent to thymine, and the amount of guanine should be equivalent to cytosine. This arrangement is witnessed in both the DNA strands.  

Each of the base pairs is produced from two complementary nucleotides and they are attached together with the help of hydrogen bonds.  

lunar landing mission. apollo 11 was the first manned mission to land on the moon. the first steps by humans on another planetary body were taken by neil armstrong and buzz aldrin on july 20, 1969. the astronauts also returned to earth the first samples from another planetary body.

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